Copy and Paste Question

Sorry if this has been answered here already, as I have searched the forum and didn't find it. I have reviewed the iphone User Guide (thanks to another member for pointing this out on the Apple site), and I understand about copying and pasting. But, for some reason, I can't seem to get this magnifying glass to appear when I am trying to copy text from an e-mail or Facebook. I have a feeling that there is some little trick that I am missing. Can anyone guide me? Thanks!